The correct answer is A) three times the length of a dot. In Morse Code, the duration of a dash is defined as three times the length of a dot. This is a fundamental principle of Morse Code, as it ensures that the relative timing between dots, dashes, and spaces is maintained and allows for proper decoding of the transmitted characters. The other options are incorrect because: B) four times the length is too long, C) twice the length is too short, and D) one and one-half times the length is also too short to properly represent a dash in Morse Code.